1. Field
The present application generally relates to optical metrology, and, more particularly, to measuring a process parameter of a semiconductor fabrication process using optical metrology.
2. Related Art
Optical metrology involves directing an incident beam at a structure, measuring the resulting diffracted beam, and analyzing the diffracted beam to determine a feature of the structure. In semiconductor manufacturing, optical metrology is typically used for quality assurance. For example, after fabricating a structure on a semi-conductor wafer an optical metrology tool is used to determine the profile of the structure. By determining the profile of the structure, the quality of the fabrication process utilized to form the structure can be evaluated.
Optical metrology has been used to evaluate, monitor, or control a semiconductor fabrication process by determining whether the profiles of the structures formed by the semiconductor fabrication process are within acceptable tolerances. Optical metrology, however, has not been used to measure a process parameter used in performing the semiconductor fabrication process.